''It's very gusty but it looks like the strongest winds are going to start easing back.''

Compounding traffic issues, State Highway 4 near Raurimu was blocked this morning by a two-truck crash.Police said the crash happened about 3am about 500m south of Raurimu.

The two trucks got locked together side by side in the crash and could not be moved.

The road was closed to all traffic.

Heavy recovery equipment from Taupo was expected to clear the damaged trucks.

Inspector Ken Climo, of police central communications, confirmed the road closures meant the only open highways that now linked Wellington with the upper North Island were via Taranaki or Hawke's Bay - both lengthy detours.

In Christchurch a small earthquake woke some residents this morning as snow blanketed homes and streets across the city and Port Hills.

The magnitude-3.5 quake struck shortly before 7am, at 8km deep, and was centred just east of the central city, according to early Geonet reports.

The morning was clear but cold, with MetService saying cold southwesterlies would die out.